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    <title>ShellCheck: SC2325 – Multiple ! in front of pipelines are a bash/ksh extension. Use only 0 or 1.</title>
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    <h1>SC2325 – ShellCheck Wiki</h1>
    <a href="https://github.com/koalaman/shellcheck/wiki/SC2325">See this page on GitHub</a>
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    <h2
id="multiple--in-front-of-pipelines-are-a-bashksh-extension-use-only-0-or-1">Multiple
! in front of pipelines are a bash/ksh extension. Use only 0 or 1.</h2>
<h3 id="problematic-code">Problematic code:</h3>
<div class="sourceCode" id="cb1"><pre class="sourceCode sh"><code class="sourceCode bash"><span id="cb1-1"><a href="SC2325.html#cb1-1" aria-hidden="true" tabindex="-1"></a><span class="co">#!/bin/sh</span></span>
<span id="cb1-2"><a href="SC2325.html#cb1-2" aria-hidden="true" tabindex="-1"></a><span class="ot">! ! </span><span class="fu">true</span></span></code></pre></div>
<h3 id="correct-code">Correct code:</h3>
<div class="sourceCode" id="cb2"><pre class="sourceCode sh"><code class="sourceCode bash"><span id="cb2-1"><a href="SC2325.html#cb2-1" aria-hidden="true" tabindex="-1"></a><span class="co">#!/bin/sh</span></span>
<span id="cb2-2"><a href="SC2325.html#cb2-2" aria-hidden="true" tabindex="-1"></a><span class="fu">true</span></span></code></pre></div>
<h3 id="rationale">Rationale:</h3>
<p>POSIX (and Dash) does not allow multiple <code>!</code> pipeline
negations in a row. It's also logically unnecessary.</p>
<p>Use either zero or one <code>!</code>.</p>
<h3 id="exceptions">Exceptions:</h3>
<p>Scripts whose shebang declares it will run with Ksh and Bash will not
trigger this warning.</p>
<p>If you really want to negate multiple times on POSIX or Dash, e.g. to
normalize exit codes to 0 or 1, use <code>cmd || false</code> or a
command group:</p>
<div class="sourceCode" id="cb3"><pre class="sourceCode sh"><code class="sourceCode bash"><span id="cb3-1"><a href="SC2325.html#cb3-1" aria-hidden="true" tabindex="-1"></a><span class="ot">! </span><span class="kw">{</span> <span class="ot">! </span><span class="fu">true</span><span class="kw">;</span> <span class="kw">}</span> </span></code></pre></div>
<h3 id="related-resources">Related resources:</h3>
<ul>
<li>Help by adding links to BashFAQ, StackOverflow, man pages, POSIX,
etc!</li>
</ul>
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    <p style='font-size: 80%'><a href="../index.html">ShellCheck</a> is a static analysis tool for shell scripts. This page is part of its documentation.</p>
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